1. Field of the Invention
The present invention relates to an air bag apparatus including a switch.
2. Description of the Related Art
Conventionally, in order to protect the driver for an automotive vehicle from an impact due to a collision and the like, an air bag apparatus disposed in a boss portion (a center pad portion) of a steering wheel has been known. The air bag apparatus is provided with an inflator for generating a gas, a bag-like air bag housed in a folded manner, a module cover (a center pad) for covering the air bag, and a base plate to which the inflator, the air bag and the cover body and the like are mounted. Then, the air bag apparatus is structured such as when a gas is released from the inflator, the cover breaks along a predetermined tear line (a breaking line) from the pressure due to the expansion of the air bag so as to open like a door, projecting the air bag from the cover to expand and deploy on the side of the occupant, at a time of detecting a collision of the vehicle.
Further, a switch for operating a horn and the like has been conventionally assembled in the pad body arranged in the boss portion, and combined with the air bag apparatus in the vehicle, and operability can be improved by assembling the switch in the cover body of the air bag apparatus positioned in the boss portion.
Furthermore, since a door piece portion from which the air bag expands and projects from the cover, a switch mechanism capable of turning between an ON and OFF state with a suitable operational feeling without affecting the formation and a opening of the door piece portion, that is, a smooth deployment is desired.
In this view, for example, an air bag apparatus described in Japanese Patent Application Laid-Open No. 7-40838 has been known. In this structure, a membrane-like switch (a membrane switch) is mounted inside under the surface of the cover, the back surface of the membrane switch is covered by a rigid panel (a back panel), and a peripheral edge portion of the rigid panel is fixed to the cover body. Then, it is structured such that when the cover body is pressed, the membrane switch is pressed through the cover body, thereby closing a circuit.
However, in the structure described in Japanese Patent Application Laid-Open No. 7-40838, the switch and the rigid panel are mounted to the cover body which is torn at a time when the air bag expands so as to deploy, thereby forming three layers, and the rigid panel is mounted only to the cover body at a plurality of fastening points. Accordingly, it is necessary to mount the switch and the rigid panel to the cover body firmly and reliably, while also it being necessary that the three layers smoothly and rapidly deploy outward at a time when the cover body tears, this causes a problem increasing manufacturing cost due to complication of structure, an enlargement of a size, an increase in assembly time, and a difficulty of design. Further, there is a problem in that it becomes difficult to make whole of the air bag apparatus compact in order to retain the flexibility of the door piece portion of the cover and the space occupied by the switch is increased.